This invention relates to a process for the removal of a solute from a solution. Such a process is especially useful when the solute is a reaction by-product and is being removed from a reaction solution.
It has long been recognized that some equilibrium reactions, e.g., condensation reactions, can be driven to completion by removing from the reaction mix one or all of the reaction by-products. Such removal is not difficult if the reaction mix is solely a liquid. In these cases, the liquid by-product is removed by adding, to the reaction mix, a solid removal agent, such as a powder-type molecular sieve, which is specific for capturing to itself the by-product sought to be removed. Once the by-product capture is achieved, simple solid-liquid separation is used to separate the reaction mix from the removal agent and its captured by-product. The separated removal agent may be regenerated and returned to the reaction mix for further duty.
If the reaction mix is a liquid-solid mix and the solid is the by-product sought for removal, then conventional liquid-solid separation is useful. However, if the solid is the product sought and the by-product is a solute in the liquid phase of the reaction mix, then a difficult problem is presented. The addition of a solid removal agent to remove the liquid by-product is not an attractive solution as it is difficult, in many cases, to separate the solid product from the solid removal agent and its captured by-product. In the alternative, the liquid phase of the mix can be subjected to distillation techniques to effect removal of the by-product from the liquid phase. Such techniques, however, are not always efficient and inexpensive--indeed, the contrary is the case when the by-product and the liquid phase have similar boiling points.
It is therefore an object of the invention to provide a process for the efficient removal of a solute from a solution. It is a further object of this invention to effect such removal even when solids are present in admixture with the solution. It is still a further object of the invention to provide a process for driving an equilibrium reaction towards completion by efficiently removing from the reaction system at least one of the reaction by-products even when the reaction system is a liquid-solid mix and the by-product is a solute in the liquid phase of the mix.